Combine the butter and powdered sugar in a large bowl. Beat with a mixer until light and fluffy. Add the egg and egg yolk and beat on medium speed until combined. Add the vanilla and beat again.
With the mixer on low speed, slowly add the flour and salt. Press the dough between two sheets of wax paper or plastic wrap and refrigerate for 1 hour.
Preheat oven to 350°F. Line a baking sheet with parchment paper or a silicone baking mat.
Roll out the dough 1/8″ thick onto a baking mat, parchment paper or a well floured surface. Press the cookie cutter into the dough and carefully move to the baking sheet. Repeat until you have 32 cookies.
Bake for 8 to 10 minutes, or until the edges are slightly light golden. Remove from the oven and allow to cool on the pan for 2 minutes. Then transfer to a cooling rack.
Once the cookies are cooled, spread the raspberry jam onto the back side of the cookies. Press another cookie gently on top. Then whisk together the icing ingredients in a small bowl until it is smooth and glossy. Use a small spatula to frost the top of the cookies. Add a heart sprinkle to the center if desired.
These cookies will keep in an airtight container for 1 week or in the freezer for up to 3 months.To make traditional empire biscuits, use a circular cookie cutter and add a small maraschino cherry on top.